1. Field of the Invention
This specification relates to a circuit breaker with an arc extinguishing mechanism, and particularly, to a circuit breaker with an arc extinguishing mechanism for extinguishing arc generated when a movable contactor is separated from a stationary contactor due to a fault current.
2. Background of the Invention
A circuit breaker is an electric device for protecting a circuit and a line by automatically breaking such circuit or line upon occurrences of an electric overload state or a short-circuit state. In general, current flowing over an electric circuit is generally divided into a rated current and a fault current which flows due to a breakdown like short-circuit, grounding, etc.
The fault current is drastically larger than the rated current, so it is difficult to be cut off. Accordingly, the circuit breaker is designed to block both the rated current and the fault current. A rated switch is able to merely block a current, which is as low as the rated current, so it is distinguished from the circuit breaker. An electric power system includes a power generator, a transformer, a power transmission line and the like. When desiring to suspend some of them, a current of the power generator or power transmission line desired to be suspended is blocked by a circuit breaker such that the power generator or power transmission line can be isolated from the electric power system. Also, when a breakdown such as short-circuit or grounding is caused in the system, an extremely large fault current flows over the system. If the system is left in that state, it may aggravate damage on the broken component or portion and the other may also be out of order due to large current. Thus, the circuit breaker is used for blocking the broken portion.
In general, the circuit breaker exhibits more excellent current limitation when it has superior arc extinguishing capability and takes a shorter time to break current. FIG. 1 is a schematic view showing a structure of the related art circuit breaker, FIG. 2 is a disassembled perspective view showing a structure of an arc extinguishing mechanism of the related art circuit breaker, FIG. 3 is a view showing operations of the related art arc extinguishing mechanism, and FIG. 4 is a planar view showing an exhausting direction of arc generated from the related art circuit breaker.
As shown in FIG. 1, the related art circuit breaker 100 includes a first stator 110 implemented as a conductor to induce current to flow inwardly, a mover 130 selectively contactable with the first stator 110 by a mechanical operation of a switching mechanism 120, an arc extinguishing mechanism 140 to extinguish arc generated between contact points of the mover 130 and the first stator 110, a connecting contactor 150 coupled with one end of the mover 130, a second stator 160 connected to the connector 150 and implemented as a conductor to induce a current to flow outwardly, a trip mechanism 170 to operate the switching mechanism 120 by detecting a generation of a fault current and abnormal current, and a handle 180 to manually drive the switching mechanism 120.
As shown in FIG. 2, the arc extinguishing mechanism 140 of the related art circuit breaker 100 includes a first stator 141 and a mover 142. A stationary contact 141a and a movable contact 142a are brazed at the first stator 141 and the mover 142, respectively. A rear end of the stationary contact 141a is embossed to act as an arc runner 141b. A position adjacent to the first stator 141 and the mover 142 is shown having an arc chute 143. The arc chute 143 includes a plurality of grids 143a made of a metal having ferromagnetism, and fixing plates 143b made of an insulating material to fix the grids 143a. The first stator 141, the upper grid 144 and the arc chute 143 are integrally assembled together and mounted in a case 145 made of an insulating material.
An operation of the arc extinguishing mechanism of the related art circuit breaker is described as follows.
Referring to FIG. 3, in the related art circuit breaker 100, the stationary contact 141a and the movable contact 142a remain contacted while a rated current flows. However, when a fault current such as overcurrent or short-circuit current, is generated, the mover 142 is separated due to an electromagnetic repulsive force, which is generated between the stationary contact 141a and the movable contact 142a, thereby cutting off current. When the mover 142 is separated, arc is generated between the stationary contact 141a and the movable contact 142a. The generated arc is induced to the arc runner 141b to flow to the arc chute 143. The arc is segmented by the grids 143a of the arc chute 143, thereby increasing an arc voltage to be higher than a power source voltage, which limits the short-circuit current and results in extinguishing arc. Also, the arc extinguishing effect is obtained by arc extinguishing gas, which is generated from the insulating plates 143b which fix the grids 143b of the arc chute 143.
However, in the arc extinguishing mechanism of the related art circuit breaker, after arc generated due to a rotary motion of the mover 142 flows to the arc chute 143 through the arc runner 141b, when the arc is elongated within the arc chute 143, an arc column is not induced up to the upper grid 144, it is impossible to obtain a significant increase in an arc voltage. Also, the insulating plates 143b for supporting the grids 143a are unable to generate significant extinguishing gas due to arc energy. Hence, it is impossible to expect an increase in the arc voltage in response to an increase in pressure. Also, referring to FIG. 4, the arc extinguishing mechanism of the related art circuit breaker extinguishes arc merely by segmenting arc into various directions a, b, c by the grids 143a and cooling arc, so it takes a long time to extinguish arc and also arc heat gas is reversely exhausted in a direction d where the rotational shaft of the mover 142 is installed, which causes problems of arc reignition and damage on the movable contact 142a and the stationary contact 141a. 